This invention relates generally to turbomachinery, and specifically to rotor blades for the compressor, turbine or fan section of a gas turbine engine. In particular, the invention concerns a rotor blade with a bonded cover.
Gas turbine engines are typically built around a power core made up of a compressor, combustor and turbine, arranged in flow series with an upstream inlet and downstream exhaust. The compressor compresses air from the inlet, which is mixed with fuel in the combustor and ignited to generate hot combustion gas. The turbine extracts energy from the expanding combustion gas, and drives the compressor via a common shaft. Energy is delivered in the form of rotational energy in the shaft, reactive thrust from the exhaust, or both.
Turbine engines (or combustion turbines) provide reliable, efficient power for a wide range of applications, including aviation and industrial power generation. Small-scale turbine engines generally utilize a one-spool design, with co-rotating compressor and turbine sections. Larger-scale jet engines and industrial gas turbines (IGTs) are typically arranged into a number of coaxially nested spools, which operate at different pressures and temperatures, and rotate at different speeds.
The individual compressor and turbine sections in each spool are subdivided into a number of stages, which are formed of alternating rows of rotor blade and stator vane airfoils. The airfoils are shaped to turn, accelerate and compress the working fluid flow, and to generate lift for conversion to rotational energy in the turbine.
Gas turbine engines for aviation include turbojet, turbofan, turboprop and turboshaft designs. Turbojets are an older design, in which thrust is generated primarily from the exhaust. In modern applications, fixed-wing aircraft typically employ turbofan and turboprop engines, in which the low pressure spool is coupled to a propulsion fan or propeller. Turboshaft engines are used on rotary-wing aircraft, including helicopters.
In turbofan engines, the fan rotor typically operates as a first stage compressor, or as the pre-compressor stage for a low-pressure compressor or booster module. Fan and compressor blades are thus subject to similar design considerations, and the term compressor blade may encompass both fan and compressor airfoils. Turbine blades also share some of the same basic requirements, including the need for strong, durable and impact-resistant airfoil designs, in lightweight, cost-effective configurations that improve engine performance, increase service life and raise overall operating efficiency.